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This is an archived website which has not been updated since 2002. Some information may be inaccurate or out of date. |
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Are old TVs easy to renovate and repair?
Generally yes - they are not very complicated or intricate inside. There is no real shortage of valves and other spares either. Only some picture tubes are hard to find now.
Surely there are no programmes on the 405-line system now – so do you watch blank screens?!?
No, because it's no great problem getting 405-line TVs to work with programmes recorded on a VHS (or Betamax) recorder. Most VCRs will record and play back 405-line material quite well, even though they were not designed to do this. Obviously the TV must be in good working order, then all you need do is build or buy a modulator which translates the video signal from your recorder onto a VHF channel suitable for the TV. Your video recorder already has a modulator which puts out a signal on channel 36, but 405-line TVs don't normally have UHF tuners, so you need to make a VHF modulator. Also it has to be positive modulation, with AM sound, but those finer points are all covered in the design details.
Modulators are sometimes available from Radiocraft and are discussed in greater detail here.
Why not just convert the old sets to work on the current 625-line system?
It is generally not a feasible project to convert an old 405-line set to work on 625 lines, or rather, it’s as much work as converting a gas cooker to electric! The process is expensive and destroys the sets' authenticity. Would you put a new Formica surface on top of an antique oak kitchen table? Most collectors would not do this kind of thing ... Better to use a standards converter and watch in 405-lines (admittedly this will cost money, say just over £300) or you could have the original chassis removed and the ‘innards’ of a modern black and white set substituted. This is what is done for old sets that appear as props on television.
Can I have a second opinion on that?
When 625-line television came on in the UK in the early 1960s there were articles and books published about converting 405-line sets to 625. It is extremely difficult though, as so many functions in a TV rely on the horizontal time base frequency (25x625 = 15625Hz vs 25x405=10125Hz). The most difficult feature was the high voltage for the CRT 15 to 20kV, which is generated in a flyback transformer and also generates the horizontal deflection signal and various other lower voltages. Changing the frequency by +50% will typically blow the transformer. Any 405-line set will be black and white, it will tune only the old bands 1 and 3, not the UHF channels used by 625-line colour. Of course you could use modern technology to convert the signal. Something like use a PC tuner card to demodulate the sound and video and then use a DSP to interpolate and regenerate a B&W 405-line signal. There is nothing off the shelf that will do it. The nearest are the converters sold that change between NTSC 525-line and PAL or SECAM 625-line colour but all the hardware is in LSI chips which cannot be modified. They work by digitising the signal using A/D converters, storing multiple frames in RAM and interpolating to produce the desired output frame/line rate, finally converting back to analogue with a D/A converter. If you don't know what the acronyms and buzzwords mean don't even think about it.
from a Brit in exile - Mike Gingell, KN4BS Raleigh NC, USA
I have an old 405-line TV and wish to watch pictures on it occasionally. What's the minimum-cost way of doing this? Is there some adapter that will allow me to watch today's programmes on an old set?
First things first. Are you sure your old TV is in working order? If not, don't just plug it in to find out. If it has suffered from damp during storage (and you may not know this), it could be a fire hazard if plugged in. Certain components may fail if subjected to 250 volts, although in the hands of experts, they could be brought back to life slowly, by applying a low voltage first and gradually increasing the voltage over a period of hours.
But let's assume your set is fine (and even if not, it can probably be refurbished by a good technician – most old-established TV dealers have someone who can repair valve-era sets). The simplest way to make it show pictures again is from a VHS video recorder, not using tapes that you record or buy but using tapes which have been recorded specially in the 405-line system (we can put you in touch with people who can supply 405-line tapes). You need a special device called a Band I Modulator which will cost around £150 (unless you design and build it yourself). Then you're in business and can show pictures (but only the programmes recorded on the tape). Incidentally, there is one kind soul who advertises in 405 Alive magazine who will copy your 625-line recordings onto 405-line tape, so there isn't any problem in this respect.
If you want to go the whole hog, you'll need a standards converter that actually transforms today's 625-line pictures into 405-line images. Until recently you could buy these from a specialist supplier but production has ceased for the time being as the special ICs used are no longer available. These are not simple technology, not a simple DIY job. And don't believe anyone who tells you there's a cheaper way of doing it, because apart from finding a 405-line era TV camera (where would you find one outside a museum?) and using this to shoot the screen of your 625-line television, there isn't any cheaper way.
Note: Building your own converter is not a realistic proposition unless you already have seriously advanced design and construction facilities. It’s not a task for amateurs, not even for gifted ones. Many of the parts needed are available only from professional sources and not in one-off quantities, whilst some previous designs for converters can no longer be copied because the custom chips are no longer made.
At the moment the only person making converters is
Malcolm Everiss, 26 castleton Road, Swindon, SN5 5GD
-to whom you should send a stamped addressed envelope for details or email: malcolm (at) domino405.co.uk or visit http://www.domino405.co.uk. People who have tested it agree that it is a first-rate product, with a built-in modulator for VHF band 1 channel 1. The price is £400 post-paid.
The Pineapple and Dinosaur converters made previously are also excellent but second-hand examples of turn up very seldom (and are then sold immediately by word of mouth).
A good place to ask questions is in the 405-Chat forum on the Internet.
To subscribe to 405-Chat, send a message to majordomo (at) g7tgr.demon.co.uk with the line "subscribe 405-chat" in the body of the message (without the quotes).
Where do I get one of those electronic Test Card C generators I have seen?
Limited supplies were being sold at http://www.cix.co.uk/~rrussell/products/tccgen/tccgen.html but it appears they are now sold out.
Will any VHS recorder play and record 405-line tapes?
No but most will. Basically nearly all UK-standard PAL machines will play and make 405-line recordings, although many of the more modern machines display a ghost image of the main picture displaced to the right of the screen and some of the really new machines will not handle 405 lines at all (you’ll have to experiment). The machines which handle 405 lines best are the first-generation ‘electronic’ ones (these came after the ‘piano key’ models and were made around 1980-1982). They produce good pictures on 405 lines, without the ghost effect, and are cheap and plentiful in second-hand shops and at car boot sales. Now is the time to buy them, possibly even a second example for spares, as they will not last for ever.
Models to look out for include:
JVC (equivalent Ferguson model in patentheses)
Hitachi equivalent GEC model
New Philips VCR works fine too
"I recently bought a new video recorder for domestic use, and discovered that it beats all the machines in my shack for clean reproduction of 405 signals, the ghost echo being almost unnoticable. The machine is called Videoplus Nicam model ZX601. I understand that the same set is also sold under the Philips label."
[Dave Hooper EI2HR]
Bear in mind that to play back 405-line recordings on a standard old-type 405-line VHF television set you will need a modulator (available from Radiocraft or do-it-yourself).
Where do you find the technical information?
There are countless textbooks in libraries and second-hand book shops. There have also been several articles specifically on restoring old TVs in Television magazine. The bulletin of the British Vintage Wireless Society (incoporating 405 Alive) is full of information too and you can always have your query published in here. In fact, if you're that interested in old television, it must surely be worth your while joining in and taking out a subscription!
See also http://www.radiocraft.co.uk/vintage_television/index.shtml for some very attractive pictures of restored sets.
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